Temporal variation of the coarse sediment yield in the Wudinghe River Basin and the cause of formation
Xu Jiongxin
Institute of Geographical Sciences and Natural Resources Research,Chinese Academy of Sciences,Key Laboratory of Water Cycle and Related
Land Surface Processes,Chinese Academy of Sciences,100101,Beijing,China
Abstract Based on the data of suspended sediment yield,suspended sediment grain size,precipitation,sand-dust storms and areas of soil and water conservation measures,a study has been made on the relatively coarse(>0.05 mm) sediment yield(Qs,>0.05) in the Wudinghe River.The Qs,>0.05 shows a decreasing trend,which can be related with the decrease in annual precipitation(Pm) and number of sand-dust storm days(Pss) and the increased area of soil and water conservation measures(Atfgc).To assess the influence of precipitation and sand-dust storm on Qs,>0.05,a number of two-variable regression equations has been established,which Qs,>0.05 relates to Pss and one of the four rainfall indices: annualprecipitation(Pm),high-flow season(June-September)(P6-9),annually 1 day maximum(P1) and maximum 30 day(P30) precipitations.It has been found that the multiple correlation coefficient of the equation involved Qs,>0.05 and Pss and P30 is the largest,and the contribution of Pss and P30 to ln Qs,>0.05 was estimated as 66.5% and 33.5%.A multiple regression equation between ln Qs,>0.05 and three influencing ariables(Pss,P30 and Atfgc) has been established,which indicates that the >0.05 mm sediment yield increased with Pss and P30,but decreased with Atfgc.Thus,the decrease in precipitation and sand-dust storms and the increase in the area of soil and water consrvation measures are the cause for the decreasing trend in the relatively coarse sediment yield.
